Search Documents

By Pradip

Chelatang agents, because of their metal specificity, can function as effective mineral processing reagents. A brief review of the work carried out in this area is presented. Some of the salient features of mineral flotation and flocculation with chehting-type reagents, such as bulk us. surface chelation, the role of pH, mineral solubility, solution chemistry of reagents, and temperature, are illustrated with appropriate examples. The problems associated with the commercialization of chelating reagents for ore beneficiation and the research efforts required in this area are also discussed.

Jan 1, 1987

By M. W. Rutland, E. Manev, R. J. Pugh

Data collected from several different fundamental surface chemical techniques were compared to study the interfacial interactions in the dodecylaminelmica flotation system. In the present study, the method used was the microinterferometric free foam film technique of Scheludko (1967) in which the stability, thickness and interfacial potentials at the air/dodecylamine solution interface were determined. These results were compared to previously published data, obtained from surface force measurements (Rutland et al. 1992), in which the interaction and hydrophobic adhesion (pull-off force) between molecularly smooth mica sheets in the amine solution had been reported. Also equilibrium contact angle measurements were used for comparison. The data was collected over a range of pH values and related to the batch flotation response of mica in dodecylamine solution. It was found that maximum flotation occurred at pH 8, but this did not correlate with the minimum in double layer interaction potential. However, it appeared to correspond with a tightly packed collector monolayer giving maximum hydrophobicity to the mica surface. Finally, from the extended DLVO theory, it was shown that heterocoagulation between the bubble and the mica could only occur, providing there was a very long range hydrophobic interaction force to counterbalance the repulsive van der Waals and electrostatic forces.

Jan 1, 1995

By C. J. Pritchard, A. B. Cecala

An evaluation was performed on a district recirculation system at a trona mine in Granger, WY. A 1.52 m-diam (5 ft-diam), 37.3-kW (50-hp) vane axial fan was installed in a crosscut between the intake and return airways and recirculated about 31.4 m3/s (66,578 cfm) of air back into the intake. This amounted to a recirculation factor of about 20% of the return air. This air was part of the primary ventilation to three different continuous miner sections at operating distances of between 610 m (2000 ft) and 1829,m (6000 ft) from the recirculation fan. The mine environment was constantly monitored for respirable dust, methane and carbon monoxide in the operating sections and in the main intake and return entries. In addition, air samples were taken with and without the recirculation system during the evaluation and analyzed using gas chromatography. The results of this study showed only small increases in dust, while all other mine contaminants remained at such low levels that it was impossible to determine any relative changes from the recirculation system. Because of this, a brief SF6 tracer gas analysis study was subsequently performed to more precisely determine an increase in a mine contaminant with the recirculation system.

Jan 1, 1992

By O. R. Swendseid

The Mountain Con mine is a relatively old, deep mine located in Butte, Montana. Operations at this property through the present shaft were started before the turn of the century. As mining progressed to depth, increasing demand for ventilation facilities and changing mining conditions made it convenient to convert some nearby shafts to airways. The fact that these openings had not been originally planned for use as airways made it necessary in some instances to utilize long and inefficient already-estab¬lished entries to service working areas. This situation existed in the Lexington fresh air system. The Lexington system consists of a vertical, 3-compartment shaft extending from surface to the 3200 level and a series of 2-compartment air raises and old horizontal-haulage openings extending into a mining area several thousand feet west of the Lexington shaft between the 3900 level and the 4200 level. Because of restrictions and high resistance in the portion of the system between the bottom of the Lexington shaft on the 3200 and the mining area on the 3900, the capacity of this system is only 85,000 cubic feet of air per minute. It was calculated that the capacity of the system could be in¬creased to meet the demands of the current mining program in this section of the mine by utilizing a single, straight, horizontal air course on the 3200 and by driving an inclined air raise 740 feet long between the 3900 and the 3200.

Jan 1, 1967

By Graeme Lyall, Oy Leuangthong, Clayton V. Deutsch

There are many variables to consider in the evaluation of nickel laterite deposits including the concentrations of nickel, iron, silica, and magnesia. These variables show complex relationships with each other such as mineralogical constraints, non-linear correlation, and heteroscedasticity. The complex multivariate relationship between the variables cannot be reproduced by conventional Gaussian or indicator geostatistical techniques. We introduce the stepwise conditional transformation method as a pre- and post-processing multivariate transform for the stochastic simulation of a nickel laterite deposit. Transformed data are multiGaussian and independent at h = 0; thus, cosimulation can be avoided after verification that variables are independent at all lag distances. Back transformation restores the features of the input multivariate distribution to the simulated realizations. The complex multivariate correlations are reproduced and sensitivity issues are addressed.

Jan 1, 2002

By J. A. Finch, J. Yiantatos, A. R. Laplante

This paper re-examines the mixing conditions in the collection zone of flotation columns. These have in the past been characterized with a single uniaxial dispersion coefficient, E. The relationship between E and column diameter, Dc, is examined based on residence time distributions (RTDs) in columns of Dc ranging from 5.lcm to 184cm. Results agree with published correlations in chemical engineering, i.e. E a Dc '" , Data explain why pilot columns display significant upgrading between the feed level and the interface, whereas plant columns do not. It also suggests that, for plant columns, the full collection zone (up to the interface) can be considered when calculating the residence time. A mathematical model considering two regions of different mixing was compared to the single E model. Both models adequately fitted measured age distributions inside the column and overall RTDs. Measured and simulated mixing characteristics are compared to those of flotation banks, using a tanks-in-series approach; banks of comparable mixing to columns are identified.

Jan 1, 1988

By P. E. Richardson, N. P. Finkelstein, Z. Chen

The large band gap and insulating properties of sphalerite have limited the application of standard electrochemical techniques for studying its reactions with flotation reagents. This problem has been overcome by developing electrodes that rely on the surface conductance produced when sphalerite is activated with copper or other heavy metals. A brief exposure of the mineral in copper sulfate solutions results in electrodes that exhibit significant electrochemical activity characteristic of copper sulfides. Voltammetry studies conducted on sphalerite activated in 10-4 M CuS04, solutions at pH 4.6 provide information on both the amount and the nature of the activation product(s). It is shown that copper activation is strongly dependent on the electrochemical potential applied during activation. Activation at potentials increasingly negative of the rest potential causes a progressive increase in the amount of copper on the surface; activation at potentials positive of the rest potential decreases the amount of copper on the surface. The results indicate that both the kinetics of copper uptake and, possibly, the chemical composition (stoichiometry) of the activation product are controlled by the electrochemical potential.

Jan 1, 1995

By J. A. Chermak, D. D. Runnells

Sulfide-bearing waste rock, ore and tailings have the potential for generating acid rock drainage (ARD) when exposed to an oxidizing environment. The possibility exists of utilizing the acid produced to react with lime and/or limestone to form a self-sealing cap on the reactive waste rock and tailings. Laboratory column experiments were conducted using acid-generating waste rock with a surface amendment of limestone and/or lime. Artificial rainwater was introduced and allowed to drain through the columns. Results demonstrated that the limestone and lime reacted with the acidic rock, resulting in the precipitation of a hardpan layer of gypsum and amorphous iron oxyhydroxide at the surface. The hardpan layer significantly reduced the effective permeability of the column. Based on the results of this study, it should be possible to create hardpan layers as chemical caps to significantly reduce the infiltration of rainwater and snowmelt into acidic waste rock or tailings material in the field. Unlike traditional capping methods, e.g., clay and high-density polyethylene (HDPE) covers, chemical caps should be self-healing.

Jan 1, 1998

Over the past few years, the School of Mines of Paris has carried out a program of research* on the grade-tonnage relationships in the border zones of porphyry copper deposits. The initial problem was quite difficult : how does the grade vary at the border of the known orebodies? Does it decrease regularly, or do some thresholds exist, where the grade diminishes abruptly? The answer to these questions have important repercussions on the prediction of the future reserves in the fringe of the orebodies. If the grade decreases regularly, very important reserves could exist; if not, there would be strong limitations to the possible recoverable reserves. The first step of our study was a critical study of previous work done on the subject. It appeared that, following Lasky's pioneering paper (Lasky, 1950), most of the authors used what we can call an historical approach to the problem. In this, the grade-tonnage relationships are calculated from the available figures for production and reserves and the results are then extrapolated to the future. The strong limitation of this model are brought out in this article.

Jan 1, 1982

By David L. Bradfield

This paper covers the development of the Yeelirrie Uranium Project from the discovery of the Yeelirrie deposit in 1970 to the present time, with emphasis on the mining, processing, and environmental requirements of the project. The Yeelirrie Uranium Project is managed by the "Yeelirrie Uranium Joint Venture Partnership", which, when formed, consisted of Yeelirrie Development Company Pty., Ltd., Urangesellschaft, Australia Pty. Ltd. and Esso Exploration and Production Australia Inc. The Yeelirrie Uranium Joint Venture Partnership holds mineral claims over the Yeelirrie uranium ore deposit in Western Australia. This deposit encompasses some 35 million tonnes of ore containing in excess of 50,000 tonnes of uranium as U308. Agreement has been reached with the State of Western Australia to mine and process the ore to produce uranium ore concentrate. The Project scope provides for an open-cut mine, alkaline leach hydrometallurgy plant, power plant, township, airstrip, access roads, community services and utilities. The Yeelirrie Uranium Project described herein has progressed through the stages of exploration, mine evaluation, process testing, project scope definition, environmental approval, Pilot Plant operation, preliminary engineering and the publishing of a definitive Project Feasibility Study. This article summarizes the project development through the above stages.

Jan 1, 1984

By William S. Brack

The mining industry is very capital intensive. Competition for shareholder investment has never been greater. Among our challenges is the need to meet shareholder expectations (return on investment), and one area of focus lies in our ability to deliver value on our capital investments. Our ability to meet project expectations affects not only the economics associated with the immediate project but also directly influences our ability to finance future projects. Moreover, our ability as individual companies to attract investor capital is influenced by how we have done overall as an industry, and our industry track record has not been that stellar. With safety, scope, cost, schedule, and quality as guiding principles, our project managers today must address high expectations on every project. This paper examines some items that should be on today's project management checklist. PROJECT ENGINEERING Herbert Hoover, himself a mining engineer, said Engineering is a great profession. There is the fascination of watching a figment of the imagination emerge through the aid of science to a plan on paper. Then it moves to realization in stone or metal or energy. Then it brings jobs and homes to men. Then it elevates the standards of living and adds to the comforts of life. That is the engineer's high privilege.

Jan 1, 2004

By Andrew I. Hustrulid

The discrete element method has successfully been used to model the behavior of material flow in transfer stations. With position, velocity, and applied forces for every particle and boundary in the simulation available at increments of 10-5 seconds, the next critical step is the presentation of this data in a concise and beneficial form. This paper discusses several methods of presenting the data from discrete element simulations that are used to improve the performance of a transfer station. These measurements are also used as a learning tool to better understand and visualize how material transfers from one belt to the next.

Jan 1, 1998

By A. S. Trimble, J. C. Hower

The petrographic composition of sized coal produced through the progressive grinding of a Central Appalachian high-volatile bituminous coal blend was analyzed for multiple sets either by removing fine, -200-mesh, coal after each test iteration or by retaining the fine coal in progressive test fractions. With prolonged grinding, coarser fractions tend to become depleted in vitrinite and vitrinite-rich microl ithotypes, leading to progressively harder-to-grind coal remaining in the oversize, +200-mesh, fractions. The latter trend is shown both by the maceral and microlithotype composition of the coal and by the increased slope and fractal dimension of size frequency distribution, implying an increase in hardness and resistance to grinding of the oversize coal.

Jan 1, 2000

By D. S. Holmes

Biological processes for metal solubilization and ore beneficiation are in widespread use today. There are also some promising new applications of biotechnology in the areas of metal concentration and toxic metal cleanup. Recent progress in genetic engineering promises both to revolutionize the existing biological process and to expedite the adoption of the new biological applications. But before it can do so effectively, progress must be made in many areas of fundamental research and in biochemical engineering. These issues are addressed with special reference to the biotechnology of semi-enclosed containers (bioreactors), dumps, heaps, in situ and under- ground leaching, and with respect to the biotechnology of metal concentration. Finally, certain biological considerations for bacterial strain improvement are discussed.

Jan 1, 1987

By Brian S. Prosser, Ian J. Duckworth

With the trend in the coal mining industry pushing towards improved productivity and greater production, the number and size of longwall panels is increasing rapidly. The development and mining of large longwall panels causes unique problems in the provision of adequate ventilation at the working faces. Because of the transient nature of the longwall panel, and the difficult field conditions for ventilation measurements, detailed pressure and volume surveys are often not conducted around the longwall circuit. This is unforlunate because the highest resistance airway in longwall mines is typically the longwall tailgate, which frequently represents the only unregulated split in the ventilation network. This paper examines data collected from ventilation studies of longwall panels at nine mines. The variation in airway resistance, ventilating pressure and airflow is examined and compared with specific factors such as airway dimensions, ground conditions and support type used.

Jan 1, 1997

By Michael J. Martinson

A powerful methane explosion in the mid-shaft pump station of a main service and ventilation shaft killed several persons on the station; more workers were killed when a mancage travelling down the shaft fell to the shaft bottom under a pile of broken concrete slabs from a brattice wall destroyed by the explosion venting into the shaft and a tangled mass of twisted steelwork from the equipped compartment. The newly-commissioned shaft serves a recent extension of an established mine on the Orange Free State (OFS) goldfield in South Africa. After outlining the circumstances in which the paper was written, and reviewing the nature and extent of the methane hazard in OFS mines, the paper describes the physical layout of the shaft and summarises evidence given by witnesses at the official inquiry concerning events prior to the explosion. No attempt is made to apportion blame for the incident.

Jan 1, 1989

By E. Topuz, M. J. McPherson, I. M. Konduri

The research is carried out to investigate the flow mechanics and effectiveness of face ventilation using induction fans, as an effort to provide a more efficient alternative to conventional auxiliary duct or brattice ventilation systems. The induction effects and plume longevity of fluid jets are being studied with the help of a plexi-glass model, using water as the fluid medium and creating a system that is dynamically similar to the flow in mine headings. This scaled model represents a typical 1.5m x 6m x 25m heading connecting to a crosscut. Reynolds Number criteria are used to obtain dynamic similarity of the flow in the designed model to simulate real mining conditions. The role of various parameters such as nozzle position in three dimensions, airway roughness, nozzle geometry, and flow rate in the jet are studied. During the laboratory tests, flow visualization techniques, coupled with still and video photography, were employed to identify the flow patterns. The results indicate that in typical coal mine headings, jet fans can produce effective face ventilation for distance up to 30 meters.

Jan 1, 1995

By C. A. Pickles, D. Mallette

Silicon nitride (Si3N4 ) is an advanced structural ceramic materia1 which is presently being considered for a number of potential engineering applications, particularly in heat engines, gas turbines, and electronics. With respect to other structural ceramics, silicon nitride has relatively low thermal conductivity and thermal expansion coefficients and a moderate elastic modulus. Thus, during thermal cycling the stresses developed in this material are lower than in other structural ceramics. At the present time silicon nitride is produced via three main processes: thermal decomposition of silicon imide or amide, treatment of silicon tetrachloride or silane vapour with ammonia and nitriding of silicon powder. These three methods of production are discussed with particular attention to the effect of morphology and phase content on the properties of the final product. In this work carbothermal production of silicon nitride has been studied in a high temperature resistance furnace. Compacted briquettes of silica and carbon were produced which were reacted in a nitrogen atmosphere. The optimum reaction temperature and the carbon to silica ratio were found to be 1425OC and ten to one, respectively. The presence of large amounts of ash in the reductant promoted the formation of silicon nitride. The specific surface area of the briquettes did not have a large effect over the range studied in the present work. Briquette seeding with small amounts of Si3N4 was effective in increasing the reaction rates.

Jan 1, 1990

By A. D. Paul, Yoon R. H., C. I. Basilio

Considerable amounts of Fe3+ ions are released into solution when coal is exposed to 1-3 M acid solutions. These ions superficially oxidize the coal surface, and are reduced to Fe2+ ions. When provisions are made to generate the Fe3+ ions in solution, e.g., by inserting an anode whose potential is above the reversible potential for the Fe3+/Fe2+ couple, considerable amounts of mineral matter are liberated from the coal matrix. With many eastern U.S. bituminous coals, this mineral liberation is achieved selectively without significant breakage of the coal. It is believed that this process is induced by the osmotic pressure set-up in the crevices between the mineral matter and coal that are exposed to the solution. A theoretical model predicting the osmotic pressure is presented in this work, along with some results obtained with different coal samples.

Jan 1, 1992

By D. W. Fohlen, B. A. Filas

The International Finance Corporation (IFC), the private investment arm of the World Bank Group (WBG), requires all IFC-financed projects to comply with its environmental and social policies and guidelines. IFC's review process involves an environmental and social assessment and the implementation of an Environmental Action Plan (EAP) that will set forth the necessary actions to bring the operation into compliance. This paper provides an overview of the environmental and social policies and guidelines that apply to mining projects and examines how WBG/IFC policies and guidelines are applied to mining projects in developing countries. In addition, it includes a review of the increased emphasis IFC is giving to social issues over the past several years based on the existing WBG policies. IFC’s process for the environmental and social review of proposed investments is briefly discussed. The paper focuses on how IFC emphasis has shifted from the traditional environmental and impact mitigation analyses of a few years ago to the integrated social and environmental awareness, action (EAP), and implementation programs (social plans) required today. Today, IFC's focus is to promote sustainable development by investing in projects that directly benefit local communities and the environment. Examples of these changes will be highlighted by a review of recent investments located in West Africa. The goalposts have not moved, but the rules of the game have become tougher.

Jan 1, 2001